What Is a Machine Reamer?
A machine reamer is a type of reamer used for hole finishing on a machine tool. Unlike a hand reamer, which is used for hand finishing, a machine reamer has a straight or tapered handle (shank). It can be attached to a tool (chuck) that holds the blade on the machine.
The shape of the blade is straight, and the machine reamer consists of a blade section that cuts a hole at the cutting edge and a “burnishing section” behind the blade that crushes and smoothes out surface irregularities.
Uses of Machine Reamers
The basic use of a reamer, not limited to machine reamers, is as a finishing hole tool to improve hole accuracy after drilling.
They can produce high roundness and surface roughness that cannot be achieved with drills or end mills, as well as inside diameter dimensions that have strict standards. They are used for holes to insert positioning pins in molds, for machining sliding parts such as shafts of engine parts, and for machining injection ports such as nozzles.
Since reamers process according to the pre-drilled hole, it is important to select an appropriate pre-drilled hole diameter.
Principle of Machine Reamers
The mechanism of a machine reamer is to prepare the hole with the burnishing section while machining the hole with the cutting edge, which allows for high hole accuracy. However, a reamer by itself cannot drill a hole, and if the downhole is small, chips will clog the blade, making it impossible to process the hole.
On the other hand, if a hole is drilled at the very edge of the reamer finish to reduce the load, the surface roughness will not be good because the burrs and scratches created during the drilling process will not disappear.
Furthermore, it will not be possible to correct a slightly oval-shaped hole, so the pre-drilled hole is often drilled 0.2 to 1.0 mm smaller than the finished dimension.
Broach reamers are also used in the same manner and for the same purpose, but instead of a straight edge, the broach reamer has a twisted blade. The broach reamer is used for finishing through holes because chips are discharged forward. The twisted shape also prevents chips from clogging, enabling machining with good surface roughness, but its disadvantage is that it is a little expensive.